A few thoughts:
- To get a type rating on a multi-crew aeroplane you need CPL + ATPL writtens + IR
- You can add an IMC to a CPL with (in theory anyhow) 5 hrs training + test, no written exam. In UK airspace, that does give you a lot more capability.
- Realistically, you are up against shedloads of hour builders who'll work for nothing in things like parachute dropping.
- Glider tugging will almost always only go to pilots with significant gliding experience, and most won't get paid for it.
- The best add-on (apart from the IMC) to a CPL is probably the CRI; but that is only really useful if you have a lot of true flying experience (types, places, types of flying...) that pilots will actually want to tap into. If all your experience is on standard club-type flying and types, it's probably of limited use. If you have a few hundred hours on vintage taildraggers, you're a bit better off.
- Single pilot aircraft, being flown double pilot within an AOC (say, a Do228) do not require ATPL+IR to fly right hand seat, but they will still require an expensive type rating.
G